FIG. 4 is a view showing a conventional alignment stage apparatus applied to an exposure apparatus. The conventional alignment stage apparatus has linear motor coils 104, which are four-phase coils, arrayed on one straight line to drive a stage. The linear motor coils 104 are supported by a coil support member 103 fixed to a surface plate (not shown) in a vacuum chamber 112. A pair of guides 102 are arranged in a direction parallel to the direction along which the linear motor coils 104 are arrayed. A stage top plate 101 is attached to the guides 102 through bearings 106. The stage top plate 101 is freely guided by the guides 102 in the direction along which the linear motor coils 104 are arrayed. A moving magnet 105 is attached to the stage top plate 101 through a moving magnet connecting member 113. The moving magnet 105 includes four pairs of permanent magnets, the polarities of which alternate in the direction along which the linear motor coils 104 are arrayed. A laser interferometer measuring mirror 107 is arranged on the upper surface of the stage top plate 101 to detect the position of the stage top plate 101. In the vacuum chamber 112, as power lines 108, fluoroplastic-based wires, and the like, which are heat-resistant and generate comparatively fewer gases, are generally used (for example, see Japanese Patent Laid-Open No. 2000-227358). The power lines 108 extend to the outside of the vacuum chamber 112 through a feed-through connector 109. In this manner, an alignment stage apparatus 400 is arranged in the vacuum chamber 112.
A coil selector 110 is arranged outside the vacuum chamber 112. FIG. 5 is a view schematically showing the arrangement of the coil selector 110. In the coil selector 110, switches 114 are arranged in series with the respective linear motor coils 104. The switches 114 include mechanical contact relays or switches like semiconductor switches, i.e., FETs (Field-Effect Transistors). The switches 114 perform switching appropriately in accordance with the positional relationship between the moving magnet 105 and linear motor coils 104. A driver 111 is connected to the input of the coil selector 110. The driver 111 supplies a control current to a selected linear motor coil 104 in response to a control command, to control alignment of the stage. The coil selector 110 serves to turn on/off the switches 114 in accordance with a coil select signal to supply a current to a desired linear motor coil 104. When drivers 111 are provided to the respective linear motor coils 104, the number of drivers 111 increases in proportion to the number of linear motor coils 104.
FIG. 6 shows an arrangement of a case wherein the coil support member 103 of FIG. 4 operates as a counter mass 115. Bearings 106 are arranged on the lower surface of the counter mass 115. As indicated by an arrow in FIG. 6, when the counter mass 115 is driven in a direction opposite to the direction in which the stage is driven, the counterforce from the stage can be canceled.
In Japanese Patent Laid-Open No. 2000-227358, as the power lines 108, the fluoroplastic-based wires, which emit fewer gases, are used. As the lengths of the power lines 108 increase, however, the generated amount of emission gases becomes non-negligible. In particular, in a semiconductor device that requires an ultrahigh vacuum, the generated amount of emission gases must be minimized.
As shown in FIG. 5, the number of the plurality of power lines 108, which electrically connect the linear motor coils 104 and the switches 114 of the coil selector 110, increases in proportion to the number of linear motor coils 104. Therefore, when the number of linear motor coils 104 increases, a large number of power lines 108 must be arranged in the vacuum chamber 112. Furthermore, the number of pins of the feed-through connector 109 increases, and accordingly, the size of the feed-through connector 109 increases. Consequently, the size of the vacuum chamber 112 increases, and an increase in cost cannot be avoided.
When the coil support member 103 of a linear motor 119 operates as the counter mass 115, the counter mass 115 moves as it is driven by the stage. Hence, as shown in FIG. 6, a large number of power lines 108 is dragged in the vacuum chamber 112. Disturbance and vibration from the large number of power lines 108 degrade the alignment accuracy and posture accuracy of the alignment stage apparatus 400.
The present invention has been made in view of the above problems, and has as its object to provide an alignment stage apparatus that generates fewer gases in a vacuum atmosphere to achieve a high vacuum degree and can realize a high alignment accuracy, which is not influenced by cable disturbance and vibration.
According to the first aspect of the present invention, there is provided an alignment stage apparatus comprising a linear motor including a plurality of coils to drive a stage, and a coil selector which selectively energizes the plurality of coils, wherein the linear motor and coil selector are arranged in a vacuum chamber.
According to the second aspect of the present invention, there is provided an exposure apparatus comprising an optical system, which is arranged in a vacuum chamber and projects exposure light to irradiate a master having a pattern, onto a substrate, and the above stage apparatus, which holds and aligns the substrate or master.
According to the third aspect of the present invention, there is provided a semiconductor device manufacturing method comprising a step of exposing a pattern onto a substrate by using the above exposure apparatus, and a step of developing the substrate on which the pattern has been transferred in the step of exposing.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.